An iron flask is a magic item that can be used to trap a powerful entity in it. The drow brought an iron flask containing Maegara to the fire giants in Ironslag.[1] The drow emptied Maegara out of the flask and into Ironslag's magic forge. On the way out, they tried to trap Kuharik in the flask, but fail. They surrendered to the waffle crew and handed the flask over to Diath. Kozin told Diath the command word to activate the flask.[2] Diath was able to sneak into Ironslag and trap Maegara in the flask once more. He decided to try to free the dwarf slaves of Ironslag, using Maegara to melt their locks, but when Maegara was freed, they all burned to death.[3]
At the end of the battle of Ironslag, Strix trapped Kuharik in the iron flask.[4] She freed him and gave him the task of tracking some enemies. Because she forgot to specifically tell him to return, Kuharik was gone.[5]
When the heroes returned to Barovia, Strix tried to trap Paultin's shadow in the flask, but it didn't work.[6]